Swab cup cage

ABSTRACT

An oil well swab cup cage structure in which the lower ends of reinforcement wire members lie against an inner annular base ring, are surrounded by a soft metal intermediate ring displaced inwardly and shaped to lie around and between the lower ends of the wire members ad further surrounded by a hard dimensionallystable outer ring pressed over the intermediate ring to flow the metal of the latter into tighter engagement about said lower ends to hold them against displacement with respect to said inner base ring. The invention also discloses a method of making a swab cup cage structure including the steps of initially holding the wires in annular parallel orientation, inserting an inner base ring within them, surrounding them in the vicinity of the base ring with a soft-metal intermediate ring, displacing the latter inwardly around and between the wire members, and pressing a hard ring having an interfering internal diameter over the intermediate ring to further contract it on the wire members.

United States Patent 1191 Richardson 1 1 Apr. 3, 1973 [54] SWAB CUP CAGE [73] Assignee: Oil States Rubber Company, Arlington, Tex.

[22] Filed: Apr. 30, 1971 [21] Appl. No.: 139,039

Primary Examiner-Alan Cohan Assistant Examiner-Irwin C. Cohen Attorney-Alexander & Dowell [57] ABSTRACT An oil well swab cup cage structure in which the lower ends of reinforcement wire members lie against an inner annular base ring, are surrounded by a soft metal intermediate ring displaced inwardly and shaped to lie around and between the lower ends of the wire members ad further surrounded by a hard dimensionally-stable outer ring pressed over the intermediate ring to flow the metal of the latter into tighter engagement about said lower ends to hold them against displacement with respect to said inner base ring. The invention also discloses a method of making a swab cup cage structure including the steps of initially holding the wires in annular parallel orientation, inserting an inner base ring within them, surrounding them in the vicinity of the base ring with a soft-metal intermediate ring, displacing the latter inwardly around and between the wire members, and pressing a hard ring having an interfering internal diameter over the intermediate ring to further contract it on the wire members.

5 Claims, 5 Drawing Figures SWAB CUP CAGE This invention relates to improvements in reinforcement cages for elastomeric swab cups of the type used in oil well pipe strings, and more particularly relates to improved structures and methods of making them.

It is the usual practice during manufacture of swab cups of the type with which the present invention is concerned to first assemble a cage including a base and its wires, sometimes using a jig to hold the wires in axially disposed orientation. The assembled reinforcement cage and a rubber blank are then placed within a mold which displaces the rubber around the wires and shapes the cup, some part of the mold frequently holding the wires circumferentially in place during the molding operation. Depending upon the shape of the cup and the mold, the upper ends of the wires can be bent inwardly to prevent snagging of the wires during use either before or after the molding operation is completed. One of the main difficulties involved in a process of the general type just mentioned resides in the fact that the wire cage has a strong tendency to fall apart while it is being transferred from the jig in which it is originally assembled into the mold wherein the rubber is cured around the cage. This tendency makes it awkward to initially assemble the cup prior to curing and time consuming from the labor point of view, especially in assembling cups of the type wherein the wires are hooked at their lower ends and are loosely held in holes spaced around the base rings outside surface. The prior art teaches a number of different ways of holding the wires in alignment with the axis of the cup prior to and during introduction of the elastomeric blank into the cage assembly, some of these ways involving the supporting of the wires at their lower ends by some sort of captivating and aligning structure which holds the wires tightly while the cage and the rubber blank are being transferred into the mold. It is to this latter type of structure that the present invention relates.

It is a principal object of this invention to provide an improved method for making, and an improved structure for a reinforcement cage which facilitates the original assembly of the cup, holds the wires accurately in place prior to and during molding of the cup, and provides a structure which will maintain the positions of the wires with great strength when the cup is heavily loaded by fluid pressures during use in the performance of its function in an oil or other analagous well.

It is another major object of this invention to provide a structure for a reinforcement wire cage in which the cage includes an inner base ring operative to provide considerable load support for the rubber body portion of the cup, while at the same time providing radial support for the lower ends of the wire members. In accordance with the present object, the wires are held tightly against the base ring by an intermediate soft metal ring therearound, which ring is displaced inwardly around and between the wires to hold them with the proper circumferential spacing while at the same time maintaining their alignment in axial planes. In further accordance with the present object, the softmetal ring, subsequent to its shaping and inward displacement around the lower ends of the wires, is then further crushed tightly against the wires by an outer rigid ring, this outer ring directly contacting the softmetal ring.

It is still another object of the present invention to provide an improved cup structure employing a softmetal intermediate ring displaced inwardly about the lower ends of the reinforcement cage wires, taken in combination with a rigid ring which surrounds the soft ring and prevents radial expansion thereof. This is believed to be an advantageous combination from the point of view that the outer hard metal ring is dimensionally stable, and can be pressed over the soft intermediate ring with an interfering internal diameter so that the metal in the soft ring is caused to further flow inwardly between the wires as the hard ring is pressed into place. The soft ring is advantageously made of a ductile metal such as aluminum which has a great tendency to flow, and it is this ability to flow which pro vides uniform tight support of all of the wire members located inside the soft ring as a result of pressing the hardened ring thereover. On the other hand, it would not be an advantageous combination to press a hardened ring, such as the present outermost ring over top of an intermediate hardened ring in view of the fact that the underlying wires are also made of spring steel, whereby there would be no metal present which could give or flow if such an engagement were attempted. For instance, there would be no advantage in trying to press a hardened ring over the spring-steel corrugated ring 14 shown in U.S. Pat. No. 2,305,282 to Taylor in view of the fact that the metal in the corrugated ring would not be able to flow when such hardened ring was introduced thereover. Thus, it is an important feature of the applicants disclosure that he uses the combination of a hardened outer ring and a soft ductile intermediate ring which can be displaced and shaped around and between the wires.

It is another important object of the present invention to provide a structure which is capable of using a shaped ring to hold the lower ends of the reinforcement wires in the exact orientation desired, while at the same time preventing outward radial expansion of the shaped ring and consequent displacement of the lower ends of the wires when the cup is loaded by fluid pressure during actual use. In the above mentioned U.S. Pat. No. 2,305,282 to Taylor, the corrugated spring metal ring would tend to expand under load because of its corrugated configuration, and therefore the structure in the patent includes a large outer ring having a complex shape which would be expensive to manufacture, the large ring serving to support the wires at a point above the corrugated ring and thereby combat undesired radially outward displacement of their lower ends. As a result of changing the spring metal in the prior art corrugated ring to a soft metal, it becomes advantageous -to subsequently press a simple ring of rigid material over the shaped ring, thereby making a less expensive structure which at the same time has greater holding power because of the tendency of the soft metal in the intermediate ring to flow snugly about and grip the wires when the hardened ring is pressed over it.

It is another important object of this invention to provide an improved method for manufacturing a wire cage assembly for a swab cup of the type set forth above, the method including the initial supporting of the wire members near their upper ends in parallel axial relationship, inserting a base ring within the wires in the vicinity of their lower ends, and applying a soft-metal ring around the lower ends of the wire members opposite the base ring and thereby contracting the soft metal ring against, around and between the wires to hold them snugly in place against the base ring. This contracting of the soft-metal ring and the shaping of it around the wires can be accomplished either by mechanical swaging, by hydraulic or pneumatic pressure, or by the release of magnetic energy against the ring to cause it to contract. In any event when the ring has been shaped about the lower ends of the wires, the method proceeds to press over the soft ring a hardened metal ring having an inside diameter slightly smaller than the shaped outside maximum diameter of the intermediate ring to cause its metal to flow into still tighter engagement about the wires and hold them rigidly and snugly in place. The wires can then be released from their temporary support at their upper ends in view of the fact that they are now accurately supported in place on the base ring. The cage formed in the manner just set forth is fully self-supporting and can be conveniently combined with an uncured rubber blank and inserted into a mold, and thereafter cured to form a finished cup. The upper ends of the wires can be bent radially inwardly either before or after the molding operation, as desired.

As can be seen by close inspection of the particular embodiment illustrated in the present drawings, the outer rigid ring causes a wave of soft metal to flow ahead of it as it is pressed over the intermediate softmetal ring formed about the wires. In the present embodiment the wires proceed upwardly to follow the contour of an outwardly flaring inner base ring, so that the locus of the wires increases in diameter as they extend upwardly beyond the lower portion of the internal base ring. This increase in wire locus diameter is relatively abrupt and serves to limit the intermediate soft metal ring to occupying a position opposite the lower portion of the inner base ring. The outward curving of the wires above the shaped soft-metal ring not only limits its upward movement when it is inserted in place, and during swaging or shaping thereof, but it also prevents the intermediate soft-metal ring from travelling upwardly along the wires when the outer hardened ring is subsequently pressed into place along an axial path from the bottom of the cup upwardly to overlie the soft intermediate ring. Thus, the outward curving of the wires just above the two outer rings not only provides the wires with greater flexibility to bend outwardly during fluid loaded use of the swab cup, but also serves to axially position the two outer rings during manufacture.

It is another object of this invention to provide an improved structure in which the metal of the soft intermediate ring can be caused to flow into tight engagement with the wires and follow their contours partway around the wires so as to prevent them from rotating when the wire cage has been completed. Some of the prior art patents, for instance the above mentioned U.S. Pat. No. 2,305,282 to Taylor, use paired wire members wherein the wires have been bent double, and therefore have substantially no tendency to rotate in their engagements with the corrugated ring shown in that patent. However, the present structure needs the improved engagement because it uses separate and individual wires where such rotation could happen, the

use of individual wires being preferable inasmuch as each one is more nearly free to follow the internal contour of the tubing within which the swab cup is operating at any particular moment, rather than being limited in its motion by attachment at its outer end to an adjacent wire.

Other objects and advantages of the present invention will become apparent during the following discussion of the drawings, wherein:

FIG. 1 is an elevation view partly in cross-section showing a swab cup according to the present invention mounted on a mandrel and located within sucker rod tubing;

FIG. 2 is a sectional view taken along line 2-2 of FIG. I;

FIG. 3 is a perspective view partly in section of reinforcement wires disposed against the outer surface of an annular base ring;

FIG. 4 is a perspective view showing an outer rigid ring according to the present invention; and

FIG. 5 is a partly exploded view illustrative of the method of manufacturing a reinforcement cage assembly according to the present invention.

Referring now to the drawing, FIGS. 1 and 2 illustrate a swab cup generally designated by the reference numeral 10 and located within a length of sucker rod tubing T into which the swab cup fits loosely when descending but expands to seal at its upper end when being raised, in a manner well known per se. The present swab cup 10 as illustrated is supported on a mandrel M which is of conventional design, for instance similar to the mandrel shown in Bowerman US. Pat. No. 2,518,275. The mandrel is generally made by screwing together several sections, and each section includes an upper portion having a reduced-diameter shaft S and internally threaded boss B joined by a fluted central section F to a lower portion including screw threads S. The elastomeric body 11 of the swab cup includes a shoulder 12 which engages the shoulder of the fluted portion F of the mandrel M when the mandrel is being lowered through fluid located in the well tubing T. Conversely, when the mandrel is raised within the tubing, the cup 10 descends on the mandrel so that the bottom surface 13 of the cup seals against the top surface of the next lower internally threaded boss B. Ordinarily, a multiplicity of such swab cups are carried on a multiple section mandrel. The various features described so far are well known in the prior art and are believed to require no further explanation. The novelty of the present invention resides in the structure of the wire cage and the rings by which the wires are attached to form the base of the cup, and to the method of making this structure.

Referring first to the structure of the cage assembly, FIGS. 1, 2 and 3 show that the cage assembly comprises an inner base ring 15 including a lower portion 16, a central portion 17 and an upper portion 18, these portions being seen best in FIGS. 1 and 3. The base ring 15 is embedded in the lower portion of the elastomeric body 11 just above the bottom 13 of that body, and the ring 15 extends well up into the body, at least one third 7 of the way toward the upper end thereof. The lower portion 16 of the base ring is of such diameter as to lie nearer to the bore 20 of the cup than to its outer periphery 21, but the central portion 17 of the base ring flares outwardly and then joins an upper portion 18 which lies nearer to the outer periphery 21 of the cup than to its bore 20. The central and upper portions of the base ring together are as long as or longer than the lower portion of the cup, as measured in the axial direction A of the cup.

The cage assembly itself includes an annular series of axially extending, circumferentially spaced, reinforcement wire members 25, these wires being embedded in the outer peripheral surface of the elastomeric body 1 1 and extending upwardly beyond the body to terminate in upper ends 26 which in the manner of the prior art are bent generally inwardly so as to prevent their snagging upon the joints (not shown) of the tubing T. The wires can be bent at any stage during manufacture that seems desirable, namely either before or after molding of the rubber body. The wire members extend downwardly and are bent toward the center of the rubber body 11, as shown at 28, and then resume axial orientation as they approach their lower ends 27. The wires normally lie against the upper portion 18, the central portion 17 and the lower portion 16 of the base ring 15 and terminate inside of the rubber body above the lower end 13 thereof. Their lower end portions 27 are located opposite to and extend about coextensively with the lower portion of the base ring 16.

The lower ends 27 of the wire members 25 are surrounded by an intermediate soft-metal ring 30 which ring has its metal displaced inwardly as at 31 between and around the lower ends 27 of the wires to support them in axially oriented relationship. The inward displacement of the metal around the wires can be seen best in FIGS. 2, 3, and 5. The high points 32 of the soft metal ring 30 are subsequently further compressed radially inwardly so that the soft-metal is caused to flow inwardly around the wires even tighter as a result of pressing a rigid ring thereover. If the metal ring 35 is pressed upwardly from the lower end of the cage as sembly, some of the metal from the high points 32 of the soft ring is caused to flow upwardly and form a slight bead 33 above the rigid ring 35 as can best be seen in FIG. 1.

When the rigid ring 35 has been pressed over the soft ring 30 the resulting cage assembly and a charge of uncured elastomeric material 11 are inserted into a mold (not shown) and cured in a manner well known per se to form the composite cup as appears in FIG. 1.

Referring now to the method of making the wire cage, this method is illustrated in FIG. 5 and shows one suitable manner for holding the upper ends of the wire reinforcement members in annularly spaced, axially parallel, mutual relationship. These wires can be held in a very satisfactory manner by a cylindrical jig C having longitudinal grooves G in its outer surface for receiving the individual wires. The wires are held in the grooves preferably by a simple expedient such as an elastic band E, no special material being necessary in view of the fact that the cylindrical jig and the elastic band are both removed prior to insertion of the cage assembly together with a charge of elastomeric material into the curing mold. The lower portion of each of the wire members 25 is shaped inwardly and downwardly as shown in the figures prior to assembly, completion of the shaping of the lower ends being necessary in order to provide uniformity of the wire members and also because of the fact that the wire members are made of spring steel which is not easily deformed. With the wires secured in the grooves G shown at the top of FIG. 5, the inner base member 15 is inserted within the lower ends of the wire members and the latter are rotated until they lie tightly against the annular base ring 15. The soft-metal intermediate ring 30 is then slid over the lower ends of the wire members 25 until it abuts the curved portion 28 of each wire member which tapers outwardly, and the ring 30 then lies in a position which is about coextensive with the lower portion 16 ofthe base ring 15.

The next step in the process is to apply radially inwardly directed pressure, in the direction of the arrows P in FIG. 5, in order to displace the soft metal of the ring 30 inwardly to produce low portions 31 between the lower ends 27 of the wire members 25. Naturally, these metal-displacing forces are applied simultaneously and uniformly against the outer surface of the ring 30 midway between each of the lower ends of the wires 27 so as to displace the soft metal of the ring 30 inwardly in a uniform manner. The axial length of these lower ends 27 and of the ring 30 is selected great enough to accurately hold the wire members 25 in accurate longitudinal alignment. These pressures along the arrows P can be applied either by mechanical fingers pressed inwardly toward the axis A of the cage assembly, or else they can be applied by hydrostatic, pneumatic, or even magnetic forces, all of which are known in the prior art.

Finally, in order to complete the cage assembly according to the present invention a rigid ring 35, having an internal diameter which is somewhat less than the outer peaks 32 of the soft ring 30 when formed, is pressed over the intermediate ring 30 so that it further displaces some of the material of the ring 30 from the vicinity of the outer peaks 32 in toward the valleys 31 between the wires, the ring 35 also displacing some of the material from the peaks 32 upwardly against the bend portions 28 of the wires as shown at 33 in FIG. 1. The rigid ring 35 thus not only prevents expansion of the softer ring 30 during heavy fluid loading of the cup in a well, but it also has the effect of further tightening the grip of the soft-metal ring 30 on and about the lower ends 27 of the wire members 25. As used in this context, the words soft-metal are intended to specify an unhardened metal which has substantial ductility, for instance a mild steel ring being useable in place of aluminum.

The cage assembly is now ready for the molding step, except for the removal of the cylindrical jig C and the elastic band E from the upper ends of the wires. As stated above, the tops of the wires can be bent inwardly as shown at 26 in FIG. 1 after the cup has been molded, or before molding, depending on manufacturing expediences.

The present invention is not to be limited to the exact form shown in the drawing, for changes may be made therein within the scope of the following claims.

I claim:

1. An improved reinforcement cage assembly for a well swab cup including an annular body of elastomeric material having an axial bore therethrough for receiving a supporting mandrel, said assembly comprising:

a. an annular base ring embedded in the body near its lower end and surrounding the bore;

b. reinforcing wire members disposed axially of the body and embedded in its outer periphery in circumferentially-spaced mutual relationship therearound, the wire members being curved inwardly and at their lower ends lying against the outer surface of said base ring;

0. an intermediate ring of soft metal surrounding the lower ends of the wire members opposite the base ring, the soft-metal ring overlying said lower ends and being displaced inwardly between the wires to 10 support them in axially oriented relationship; and

d. a rigid metal ring surrounding the soft-metal ring in tight contact with it where it overlies said lower ends and preventing radial expansion thereof and of the lower ends of the wire members.

2. In an assembly as set forth in claim 1, said base ring having a lower portion lying parallel and closely adjacent to the bore and having a central portion curving outwardly away from the bore and having an upper portion lying parallel to the bore and nearer the outer periphery of the cup body, and the wire members being shaped to lie against the lower, central, and upper portions of the base ring.

3. In an assembly as set forth in claim 2, the base ring extending at least one-third of the way up the cup body as measured in the axial direction.

4. In an assembly as set forth in claim 2, the softmetal ring and the rigid ring being approximately coextensive as measured in the axial direction with said lower portion of the base ring, and the wire members curving outwardly toward the outer periphery of the body just above said rigid ring.

5. In an assembly as set forth in claim 4, the central and upper portions of the base ring being at least as long in the axial direction as the said lower portion, 

1. An improved reinforcement cage assembly for a well swab cup including an annular body of elastomeric material having an axial bore therethrough for receiving a supporting mandrel, said assembly comprising: a. an annular base ring embedded in the body near its lower end and surrounding the bore; b. reinforcing wire members disposed axially of the body and embedded in its outer periphery in circumferentially-spaced mutual relationship therearound, the wire members being curved inwardly and at their lower ends lying against the outer surface of said base ring; c. an intermediate ring of soft metal surrounding the lower ends of the wire members opposite the base ring, the soft-metal ring overlying said lower ends and being displaced inwardly between the wires to support them in axially oriented relationship; and d. a rigid metal ring surrounding the soft-metal ring in tight contact with it where it overlies said lower ends and preventing radial expansion thereof and of the lower ends of the wire members.
 2. In an assembly as set forth in claim 1, said base ring having a lower portion lying parallel and closely adjacent to the bore and having a central portion curving outwardly away from the bore and having an upper portion lying parallel to the bore and nearer the outer periphery of the cup body, and the wire members being shaped to lie against the lower, central, and upper portions of the base ring.
 3. In an assembly as set forth in claim 2, the base ring extending at least one-third of the way up the cup body as measured in the axial direction.
 4. In an assembly as set forth in claim 2, the soft-metal ring and the rigid ring being approximately coextensive as measured in the axial direction with said lower portion of the base ring, and the wire members curving outwardly toward the outer periphery of the body just above said rigid ring.
 5. In an assembly as set forth in claim 4, the central and upper portions of the base ring being at least as long in the axial direction as the said lower portion. 